Geophysical investigations on the continental shelf and slope north of Scotland

Abstract

A gravity, magnetic and seismic reflection survey of the continental shelf and slope around the Orkneys, Hebrides and Shetlands was completed by Durham University on RRV John Murray in 1968. The Bouguer gravity anomaly map shows a large gravity ' high' reaching 94 mgal which is continuous for 155 miles (250 km) and tends approximately NNE. across the shelf. This is interpreted as being due to a seaward extension of Lewisian basement rocks exposed on the Scottish mainland. Large amplitude gravity ' lows' also occur on the shelf and slope. A gravity ' low' 56 miles (90 km) west of the Shetlands has been interpreted as being due to a deep sedimentary basin infilled by Mesozoic-Tertiary sediments and bounded on its SE. margin by a large normal fault. Recent sediments form the continental slope which gently truncates the older Caledonian structures observed on the shelf